Soft dosage forms are widely used in a variety of consumer products. For example, many soft confections have been marketed with commercial success due to consumer preference. Further, pharmaceutical manufacturers have also developed oral dosage forms that provide alternatives to the traditional, swallowable solid tablets. These alternative dosage forms, which for example include chewable or orally disintegrable tablets, are often easier and more convenient to administer, especially to pediatric and geriatric patients. Softer tablets are also advantageous for applications where it is desirable to provide for the topical availability of an active ingredient in the mouth or throat to provide either local effects or systemic absorption.
In chewable dosage forms, active ingredients are often employed in the form of particles that are coated with tastemasking polymers. Such dosage forms, which possess an easier “bite-through” and superior tastemasking performance, are prepared by employing reduced compaction pressures during manufacture. Although the resulting dosage forms are generally softer, they also are disadvantageously more fragile, brittle, and thus more easily chipped. This increased fragility, or friability of soft tablets adds cost and complexity to handling and packaging of these dosage forms.
In disintegratable dosage forms, the dosage form is designed to disintegrate in the mouth without chewing. See, e.g., U.S. Pat. Nos. 5,464,632, 5,223,264 and 5,178,878. While these soft tablets advantageously disintegrate completely in the mouth prior to swallowing, they also have the disadvantage of being highly friable. Thus, this dosage form also requires costly specialized handling and packaging in order to prevent breakage.
Known methods for reducing the friability of soft chewable or disintegrable tablets include incorporation of low-melting materials in the tablet matrix. PCT Application No. WO 93/13758, for example, describes soft tablets comprising a meltable binder distributed throughout the tablet, which has been melted and solidified to improve the strength (e.g. hardness and friability) of the tablets. U.S. Pat. No. 4,327,076 discloses a soft, breakage-resistant chewable tablet compressed from particles comprising a fatty material. U.S. Pat. No. 6,258,381 describes a tablet made from a granular agglomerate comprising a mixture of at least one active ingredient and a binder. After the granular agglomerate is heated to melt the binder only at or near the tablet surface it is then cooled in order to solidify the melted binder into a substantially continuous phase. This results in the formation of a fused layer on the outside of the tablet, which reduces its friability. U.S. Pat. No. 6,277,409 describes a soft chewable tablet coated with a molten material, which is then solidified to form a protective coating that reduces the friability of the soft tablet. Although these processes yield tablets having the consumer-preferred soft tablet core and reduced friability, the high levels of coating material employed are economically disadvantageous.
Swallowable tablets are commonly coated with film coatings or polymeric coatings, such as those comprising cellulose derivatives, in order to improve their swallowability. These coatings typically surround the entire surface of the tablet. However, the coatings typically employed for swallowable tablets are not particularly suitable for use on chewable tablets or those designed to disintegrate in the oral cavity because they would hinder the dissolution, disintegration, chewability, and organoleptic characteristics, such as mouthfeel of such soft tablets.
It is also known in the art to apply an impermeable coating on only a portion of the dosage form for the purpose of controlling the surface area through which active ingredient is released from the dosage form. See, e.g. U.S. Pat. No. 5,922,342. According to one embodiment of this method, a desired modified, controlled, or substantially constant, or “zero-order”, dissolution rate is provided on the tablets by controlling the surface area of contact between the core and dissolution medium. See for example, U.S. Pat. Nos. 3,146,169; 3,851,638; 4,663,147; 4,816,262; and 6,110,500. Typical manufacturing methods for these types of dosage forms include making a core, coating the core with impermeable material, then removing a portion of the core and coating to create the area for drug dissolution. See, e.g., U.S. Pat. No. 4,803,076 (tablet press for use in the manufacture of a truncated cone-shaped, as well as an apparatus for removal of a portion of the coated dosage form). Generally, a substantial level of coating is required in these types of controlled release applications in order for the coating to function as an impermeable barrier to the passage of water and/or active ingredient therethrough. Due to the dissolution rate designed for these tablets, such impermeable coatings are not only unsuitable for immediate release applications, but they are only intended for use on hard, swallowable tablets.
A need, therefore, exists for soft, immediate release tablets that have a pleasant taste as well as low friability properties, which may be processed with standard bulk handling equipment and packaged in bottles.